Does anyone know anything about this??? "L"

It started out as green mold that eventually died and turned black.

Assuming you want to get rid of it, typically people use products with oxalic acid in them. You can spray it on and it rinses clean. I've used TSP with a little chlorine bleach and a lot of elbow grease. I'm not sure there is a perfectly organic way to clean them.

has anyone had any luck with "wet and Forget",..I heard about it on the radio,....and,saw it at Ace Hardware,..and,..then at Walmart,.."L"